There are plenty of "low-skill" jobs that nonetheless require human labor in some form because of the ability of humans -- even less intellectual humans -- to think creatively and contort themselves both mentally and physically.
Imagine a robot that does everything a school janitor can do. That simply won't exist in the near future. Sure, maybe the janitor won't have to mop large floors anymore. But there's plenty of other work to be done around a school nearly always to continue to justify their employment.